1. Field of the Invention
The present invention has to do with devices and methods for operating the wellheads of active oil and gas production wells, and relates specifically to a specialized flange for fostering safe and cost-effective change-outs of equipment at a wellhead.
2. Background
There has been an unmet need in the oil and gas extraction industries for an alternative means and method for accomplishing a wellhead change out. “Change out” refers to the removal of and replacement of one set of devices atop a completed well head with an alternative device (or devices). For example, it may be desired to replace a less-desirable ball valve or thread-on gate valve with a more reliable, heavy-duty flanged master gate valve. Formerly, devices have frequently been attached to a well head by a screwed engagement with the tubing hanger, with the tubing hanger being secured to the wellhead by a screw cap. The opening at the very top of the tubing hanger is threaded interiorly, so that devices may have a screwed engagement into the top of the tubing hanger. Conventional screw caps are annular, with a set of interior threads for screwed engagement with the threads on the exterior of the wellhead top. The top of the tubing hanger is situated between the screw cap and the top of the wellhead, so that as the cap is tightened down (by screwed connection) onto the top of the wellhead, the tubing hanger is secured in place by compression between the cap and the wellhead top. Additional equipment, such as a ball valve or the like, can then be mounted at the wellhead by means of being screwed into the top of the tubing hanger. The options for changing out equipment on the wellhead accordingly has been limited, because only those auxiliary devices having a male connection for complementary threaded engagement with the female connection at the top of the existing tubing hanger, have been suitable for installation atop the existing wellhead.